Disabled Child without medical equipment

We flew BA from Miami to Manchester via London. Due to baggage issues over the weekend, our bags were not loaded onto the flight. Those bags included a specialist car seat for my daughter's condition, without it, she can have severe consequences when travelling.

AirTag shows the bag in terminal 5 at Heathrow. Despite attempts to escalate BA has done nothing about it. No movement but they keep telling me it's 'on a flight' despite those flights having left.

Any help?